Field Of View
Field of view is the angular extent of a scene a lens actually captures, determined by both real focal length and sensor size together, not focal length alone. A wider field of view fits more of a scene in frame from a fixed shooting position; a narrower field of view fits less, magnifying whatever remains in the frame.
The same real focal length produces a different field of view on different sensor sizes, since a smaller sensor simply doesn't capture as much of the lens's projected image circle. This is exactly what crop factor quantifies, and why comparing a lens's 'field of view' meaningfully requires knowing which sensor it's mounted on, not the focal length number alone.
Frequently Asked Questions
Is field of view the same thing as angle of view?
Yes, effectively — both describe the same angular extent of a captured scene, sometimes measured horizontally, vertically or diagonally depending on the source, which is worth checking when comparing published specifications between lenses or cameras.
Does field of view change if I crop a photo afterward?
The original capture's field of view stays what it was, but the effective field of view of the final cropped image narrows, functionally similar to what a longer real focal length would have captured directly.